Lamp filament mount



Aug. 16, 1949.

R. D. EATQN LAMP FILAMENT MOUNT Filed Nov. 2, +948 Patented Aug. 16, 1949 Roland D. Eaton,

slgnor to T Huntington Park, Calm, ashnio'ol-or Motion Picture "(Borpora-J thin, Hollywood; Calif., a corporation of Maine ApplioationiNWniber 2, 1e43,*se ia1sN- s7;s7;5

12 Glaims.

" This inventionjrelatesjto supports' ior mounting a ribbon filament lamps, "such as -stroboscopic and cinematographic printing lamps where it is desirable toiprcduce aqjhigh light intensity "which may be changedquiclgly. Ribbon filaments having fast heating and cooling rates are commonly selected for sucha use Hitherto thefllarnenthas been rigidly clamped orwelded to a support mounted onthe base ordishoi the lamp. How-' ever. he l e oijfilamentso, eapor s-d i ery short owing to mechanical and thermal stresses which causethe filamer'it to crinkle a short distance from the support .an'dgfinally burn out at the crinkle boundary, furthest from th Support; Expansion of the" filament between its rigidly fimd. ends is partially responsibleior the mechanical stress. Temperature gradients along the filament alsocontribute tothe crinkling.

Objects of the present invention are to provide a way of mounting the, filament so as. tomaintain a uniform temperature'throughout its length with no sharp temperature gradients present in the mount near theffilam'ent, and to. prevent crinkling of the f lament; asa result of thermal expansion. Afurtherohjectistoprovide amount which is simple and durable in, structure and economical to manufacture} In one aspect theinventioncomprises a device for mounting aribhon filament, on 'a' lamp base involving the combination of a spring leaves oneend oi which grips, the. filament resiliently throughout la considefrable, area, attached to the base a supportjforf the leaves near the other end thereof, andzmeans for. clamping the springs. on the support, characterized in that the conductivity. from the Springstothe support is less than thatirom the} filament .tfothe springs. The term Conductivity is usled'herein to refer primarily to thermal conductivity.

In another aspect theg'rippingendof the file;- ment is spaced fromthe supporh and .intermedi:

ate portionsof thespringshridge. the space, the

conductivity from the springs to supportbeing pair of opposed less than that in theintermedi'ateportions. Pref:

erably the conductivity .frornthe springs to the support is less than ieither. that in the intermediate portions or that.,.froni'the. filament to the springs.

In another aspectan elementis interposed be and the support is less than the gripping area of of each of the springs the springs orthe-'cross-s'ectional area oh-the intermediat portions of thesprin -gs In a still further aspect the invention comprises the combination-of a pairof -opposed leaf springs for-gripping the filament'res-ilientlytherebetween throughout a considerable area near one end ofthe springs; and a support 'forthe leaves near the other end thereof,- said first'ends of the; springscurving away from Ethefilament.

For the purpose of illustration a-typieal=embcdlment of the invention "is shown in -'the drawings inwhich: i

'1 is an elevation'oi-thelamp with-part of the glass 'envel-ope'broken-away; Fig. 2 is an enlarged isorn tricviewrof the lamp, parts being broken away; Fig. 3;is an exploded isometric view ofthe i'llae mentsupport; and

Fig. l'is a top'view 'of'the filament support. As shownin Figs. 1 and 2 the lamp comprises an insulating base 'I to "which'is secureda glass envelope 2' and copper 'thimbles '3, Press fitted within the thimbles are nickel; studs which are S10ttBd1at the upper ends, Within .each of the slots H is clampeda pair of molybdenum leaf springs-6', andloosely grippe'd'bjetween;the springs is the tungsten filamentl. In Operati nelectrical current passes in one of. the thimble5;, through a stud to the clamps, thence throughgthejfilament to thelopposite clamps, andtherice through the stud to the thimble.

In Fig. 3 the filamentandfthe.supporting parts are shown in approximately 'thre'e'-'quarto, rs, 2acitual size. The tungsten, filament, isfapproxi- J mately one and one half incheslongthree-uuare ters inch wide, and 0.001finch thick; Theiwidfth oitneleaf springs Bis thesame as that oithe, filament. Preferably the slot in 'tlreriiekel'studs is about twice as long as the filament'iswidejthe Walls of the slot being machined to allow" fiat contact on nickel sheet blocks .8'which are mou'nted at one end'of the springs 15: Thenickel's'tud may be blackened-t0 promoteheat-dissipation'and copper cooling fins may be added'to the portion below the slot to further cool the stud. The bifurcated portions of the studare urged-together by stainless steel machine screws 12;"

The block 8 is approximate'ly one-quarteras 7 long as the width of the'cla'mp and" about -onesixteenth of .an inch wide. It may be cutfi'mn a 3305 inch nickel sheetbloclg. Theseblocks are. tightly clamped between the walls of the slot and .theleaf springs. Preferably theyare'wvelded qt e a pr n s-1 Thej m ks. Wi e 1' 11 1 lower conductivityand the small area ofcoritact between the blocks and the studs, serve as thermal and electrical resistance. Without the blocks the studs being cooler than the springs, would tend to cool the springs, creating sharp temperature gradients at or near the clamping ends of the springs and causing thermal distortions such as crinkling in the springs. However, when elements of low conductance, such as the blocks, are interposed between the springs and the post, owing to their high electrical resistance such elements heat up and serve to insulate the springs 1 thermally from the post. Throughout their length the springs remain at an almost constant temperature, orange hot, and temperature dropping occurs in the stud near the area of contact with the blocks. 7

Near the opposite ends of the springs from the blocks the filament is resiliently gripped between two parallel fiat surfaces I4 of the springs. This gripping is loose enough so that the filament may be moved by direct force, but not loose enough so that it may be shaken out of the springs. The filament is gripped throughout an area havingthe width of the filament and approximately onethird that length. This contact has sufficient conductivity to prevent excessive temperature drop thereat thereby avoiding excessive temperature gradients in the filament and therefore minimizing local thermal distortions. The loose gripping action of the clamps allows the filament to expand evenly throughout its length and thus prevents mechanical stresses from developing. The ends of the springs [6 are curved away from the filament so that the end of the gripping area of the springs have no burrs or other irregularities which would damage the filament. Furthermore the curved ends l6 prevent warping in the fiat portions of the springs and thermal crinkles which would also damage the filament and reduce its life.

As shown in Fig. 4 a short intermediate portion R5 of the springs bridges a space between the clamped portion 13 of the springs and the gripping portion M for the purpose of spacing the filament a short distance from the clamped ends of the springs so that distortions near the portions clamped between the two blocks will not afiect the filament.

Filaments mounted in this way have been found to have a life double that of filaments mounted in the old way. By use of the leaf springs the physical length of the high resistance filament may be shortened thus saving material and electrical power.

It should be understood that the present disclosure is for the purpose of illustration only and that this inventionincludes all modifications and equivalents which fall within the scope of the appended claims.

I claim:

1. For mounting a ribbon filament on a lamp base, the combination of a pair of opposed leaf springs for gripping the filament resiliently therebetween throughout a considerable area near one end of the springs, attached to the base a support for the springs near the other end thereof, and means for clamping the springs on the support, the conductivity from the springs to the support being less than that from the filament to the springs.

2. For mounting a ribbon filament on a lamp base, the combination of a pair of opposed leaves for gripping the filament resiliently therebetween near one end of the springs, attached to the base a support for the springs near the other end '4 thereof, the end of the filament being spaced from the support with intermediate portions of the springs bridging the space, and means for clamping the springs on the support, the conductivity from the springs to the support being less than that in said portions.

3. For mounting a ribbon filament on a lamp base, the combination of: a pair of opposed leaf springs for gripping the filament resiliently therebetween throughout a considerable area near one end of the springs, attached to the base a support for the springs near the other end thereof, the end'of the filament being spaced from the support with intermediate portions of the leaves bridging the space, and means for clamping the springs on the support, the conductivity from the springs to the support being less than that from the filament to the springs and'that in said portions.

7 4. For mounting a ribbon filament on a lamp base, the combination of a pair of opposed leaf springs forgripping the filament resiliently therebetween throughout a considerable area near one end of the springs, attached to the base a support for the springs near the other end thereof, and an ei'ement betweenthe support and said other end of conductivity lower than that from the filament to the springs.

5. For mounting a ribbon filament on a lamp base, the combination of a pair of opposed leaf springs for gripping the filament resiliently therebetween near one end of the springs, and attached to the base a support for the springs near the other end thereof, the end of the filament being spaced from the support with intermediate portions of the springs bridging the space, and an element between the support and said other end of conductivity lower than that of the intermediate portions- 6. Formounting a ribbon filament on a lamp base, the combination of a pair of opposed leaves for gripping the filament resiliently therebetween throughout a considerable area near one end of the leaf springs, attached to the base a support for the springs near the other end thereof, the end of the filament being spaced from the support with intermediate portions of the leaves bridging the space, and an element between the support and said other end of conductivity lower than that of the intermediate portions and that from the filament to the springs.

7. For mounting a ribbon filament on a lamp base, the combination of a pair of opposed leaf springs for gripping. the filament resiliently therebetween throughout a considerable area near one end of the springs and attached to the base a support for the leaves near the other end thereof, the area ofcontact between the leaves and the support being'less than the first said area.

8. For mounting a ribbon filament on a lamp base, the combination of a pair of opposed leaves for gripping the filament resiliently therebetween near one end of the leaf springs, and attached to the base a support for the springs near the other end thereof, the end of the filament being spaced from the support with the intermediate portions of the leaves bridging the space, the area of contact between the leaves and the support being less than the cross-sectional area of said portions.

9. For mounting a ribbon filament on a lamp base the combination of a pair of opposed leaf springs for gripping the filament resiliently therebetween throughout a considerable area near one end of the springs, and attached to the base a support for the springs near the other end thereof, the end of the filament being spaced from the support throughout a gap with the intermediate portions of the leaves bridging the gap, the area of contact between the leaves and the support being less than the cross-sectional area of said portions and than that of the first said area. V

10. For mounting a ribbon filament on a lamp base, the combination of a pair of clamps mounted on the base in spaced relation, a pair of leaf springs held rigidly by each of the clamps, said springs having mutually contacting surfaces at one end, and parallel surfaces near the other end for gripping one end of the filament resil- V iently throughout a considerable area, and an element between the first said ends and the clamp of lower conductivity than that of said springs and that from the filament to the springs, whereby distortion of the filament and springs as they expand when heated may be prevented and a uniform temperature may be maintained throughout the length of the filament.

11. For mounting a ribbon filament on a lamp base, the combination of a pair of opposed leaf springs for gripping the filament resiliently therebetween throughout a considerable area near one end of the springs and attached to the base a support for the leaves near the other end thereof, said one end having a surface curved away from the filament.

12. For mounting a ribbon filament on a lamp base, the combination of a pair of clamps mounted on the base in spaced relation, a pair of leaf springs held rigidly by each of the clamps, said springs having mutually contacting surfaces at a first end, surfaces curved away from each other at the other end, flat parallel surfaces adjacent said curved surfaces for gripping one end of the filament, intermediate portions between the contacting surfaces and the parallel surfaces, and an element carried on each of said first ends having one surface in contact with the clamp, said element being of conductivity lower than that of the springs and than that from the filament to the springs, whereby distortion of the filament and the springs as they expand when heated may 7 be prevented and a uniform temperature may be maintained throughout the length of the filament.

ROLAND D. EATON.

REFERENCES CITED The followingreferences are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,416,623 Donath May 16, 1922 1,863,152 Barkey June 14, 1932 

